1. Technical Field
The present invention relates to a light emitting diode, and more particularly, to a method of fabricating a light emitting diode having a stepped surface structure and a light emitting diode fabricated by the same.
2. Description of the Related Art
With various advantages such as low power consumption, vibration resistance and rapid response, a light emitting diode secures better energy efficiency than existing light sources in the related art and has been expanded in application range thereof by replacing existing light sources. In addition, together with expansion of application of the light emitting diode not only to lighting but also to displays, electronic products and automotive components, a variety of research has been carried out to improve efficiency of the light emitting diode. Specifically, in order to improve efficiency of the light emitting diode, a surface structure capable of improving light extraction efficiency is formed on a surface of the light emitting diode through photolithography to change behavior of light inside the light emitting diode.
However, epitaxial layers (active layer and semiconductor layers) formed on a large substrate can be warped due to difference in lattice parameter and coefficient of thermal expansion during growth thereof, thereby making it difficult to form a uniform surface structure only through photolithography in fabrication of a large light emitting diode. Moreover, a micrometer-scale surface structure formed through photolithography has a limit to improvement in light extraction efficiency due to internal reflection by a difference index of refraction of air upon emission of light from the light emitting diode.
In order to solve this problem, although it has been suggested in the related art that a nanoscale structure be formed on the surface structure using an alkali solution such as KOH or NaOH so as to improve uniformity of light characteristics of the light emitting diode, this technique requires chemical reaction, thereby making it difficult to control the fabrication process and the shape of the surface structure as compared with physical etching. Moreover, upon formation of a nanostructure using this technique, a hexagonal close-packed pyramid structure surrounded by {10-1-1} planes is formed through selective etching, in which a side surface angle of the nanostructure is fixed to 31.6°. However, since it is known that a light emitting diode including the nanostructure having a side surface angle of 23.4° provides maximum light output, there is a need for improvement in development of a surface structure and a process technique capable of improving light output and light uniformity of the light emitting diode.
Furthermore, as a next generation light source, a light emitting diode is required to have novel functions. In practical use, a light emitting diode and products including the same can be exposed to contaminants such as dust, which blocks extraction of light from the light emitting diode, thereby causing reduction in power efficiency thereof.